For forming battery electrodes, for example, the positive electrode of a spiral-type lithium primary battery or a laminate-type lithium primary battery and the like, an electrode slurry is used. The electrode slurry is manufactured by kneading a mixture produced by mixing a powdery electrode active material, a conductive auxiliary agent, a binder, and as necessary a viscosity improver or similar substance while applying shear stress to the mixture using a planetary mixer or the like. A carbon powder such as graphite or carbon black is generally used as the conductive auxiliary agent. In some cases, a microscopically fibrous carbon material such as a carbon nanofiber (CNF) is used as the carbon powder. In either case, the carbon powder is generally used as the conductive auxiliary agent.
“Carbon-Material Design for Conductive Material in Rechargeable Batteries”, a back number of “THE MICROMERITICS”, No. 55 (2012), pages 58 to 62, Hosokawa Micron Corporation, [online search Mar. 7, 2017]), <URL: https://www.hosokawamicron.co.jp/jp/service/micromeritics/no_55/pdf/No55_10.pdf> describes carbon powder added to slurry as a conductive auxiliary agent. Additionally, “Thin Type Primary Lithium Batteries”, FDK Corporation, [online search Mar. 7, 2017]), <URL: http://www.fdk.co.jp/battery/lithium/lithium_thin.html> provides specifications and other explanations of thin type primary lithium batteries, which are actually commercially available laminate-type storage elements.
The electrode slurry is produced by adding and kneading the binder to the powdery electrode active material and the conductive auxiliary agent. To produce an electrode plate, the electrode slurry is applied over a sheet-shaped current collector using a squeegee or similar tool.
The carbon powder used as the conductive auxiliary agent is likely to aggregate and the carbon powder is difficult to be uniformly dispersed in the electrode slurry. In the case where the conductive auxiliary agent aggregates, when the electrode material is applied over the current collector to manufacture the electrode plate, lumps of the aggregated conductive auxiliary agent (hereinafter also referred to as aggregates) possibly generate unevenness in the surface of the electrode plate. That is, the aggregates cause the formation of projections on the surface of the electrode plate. Meanwhile, in the case where the electrode material is applied over the current collector with a squeegee, when the aggregates are raked over by the squeegee and the electrode material is spread out, marks remain as recesses in the surface of the electrode plate. An uneven surface of the electrode plate can degrade the battery and cause unwanted variation in battery characteristics. Additionally, there is a possibility that the projections on the surface of the electrode plate may damage a separator, possibly resulting in an internal short-circuit.